Exactly five years ago, I was in Hue, Vietnam, the site of the Tet Offensive, an American victory that Walter Cronkite helped turn into a defeat. The Viet Cong eventually took over Hue and, said our guide, with tears in his eyes, “The revenge killings were terrible.” I thought of leftists on a rampage when I read about what the California Department of Social Services did to Foothill Christian Church Preschool in San Diego and to its director, Tiffany McHugh. The Viet Cong would have been proud of what was essentially a bloodless, but nevertheless highly effective, massacre. There are...